2001 Chrysler Van Front Guage Panel

I have a 2001 Chrysler Voyager LX. The Temp gauge goes haywire (bobbing up and down) after driving about 30 minutes. A while after that the whole panel goes off then comes back on as iff I just started the engine, complete with having the seatbelt light stay on a while. Yesterday at the end of a long trip the speedometer quit working. The needle is on the wrong side of the peg. I have been told the problem could be that the panel is failing or that the alternator is sending out too much power. What do you think?